1. Field of the Invention
The present invention relates to electronic devices such as a portable telephone.
2. Description of Related Art
A portable telephone comprises an operation-side housing 7 and a display-side housing 8 coupled to each other by a hinge mechanism 9 openably and closably as shown in FIG. 5. The operation-side housing 7 comprises a front cabinet 71 and a back cabinet 72 both made of synthesis resin joined to each other, while the display-side housing 8 comprises a front cabinet 81 and a back cabinet 82 both made of synthesis resin joined to each other.
In such a portable telephone, the front cabinet 81 of the display-side housing 8 is formed from a synthesis resin having a relatively high stiffness such as a polyamide MXD6 composite molding material, while the back cabinet 82 is formed from a synthesis resin having a relatively low stiffness such as polycarbonate.
By forming the front cabinet 81 and back cabinet 82 from such two kinds of synthesis resins, the stiffness of the entire housing increases and the engagement operation by means of the elasticity of the hook mechanism for engaging both the cabinets 81 and 82 to each other becomes smooth.
However, the portable telephone shown in FIG. 5 has a problem of having warpage in the display-side housing 8 as shown by the two-dot chain lines in the figure when exposed to a high temperature environment. This is because the synthesis resin forming the back cabinet 82 of the display-side housing 8, such as polycarbonate, has a greater linear expansion coefficient than the polyamide MXD6 composite molding material forming the front cabinet 81. In other words, when exposed to a high temperature environment, the back cabinet 82 greatly expands in a longitudinal direction thereof to warp as shown by the two-dot chain lines in FIG. 5, and along with such warpage, the front cabinet 81 also warps as shown by the two-dot chain lines in FIG. 5. This can result in a great gap between the operation-side housing 7 and the display-side housing 8.
For the problem of having the warpage on the housing and the gap between the housings as described above, conventionally, a countermeasure has been taken by modifying the cabinet structure to absorb the heat expansion of the synthesis resin. However, the electronic device on which the conventional countermeasure is taken has a problem of the growth in size and increase in weight due to the complexity of structure associated with the modification of the cabinet structure.